Characteristic parameters of photonic nanojets of single dielectric microspheres illuminated by focused broadband radiation

Herein, we report the theoretical investigation on the photonic nanojets (PNJs) of single dielectric microspheres illuminated by focused broadband radiation (polychromatic light) from a Halogen lamp, supercontinuum source, light-emitting diode, and Hg arc lamp. The role of incident beam waist, refractive index of the surrounding medium, and radius of the microsphere on the characteristic parameters such as the electric field intensity enhancement, effective width, and length of the PNJ is studied. Interestingly, the characteristic parameters of the PNJs of solid microspheres obtained for the above-mentioned broadband radiation sources are found close to those observed for the focused monochromatic radiation of wavelengths which are near to the central wavelengths of the sources. Moreover, the characteristic parameters of PNJs of the core–shell microspheres of different thicknesses (t) illuminated by polychromatic radiation from most commonly used sources such as Halogen and Hg arc lamps are studied. For each t value, a suitable wavelength of monochromatic radiation has been found to generate the PNJ with characteristic parameters which are close to those obtained in the case of polychromatic radiation. We believe that the analytical theory and the theoretical simulations reported here would be useful for researchers who work in the fields such as PNJ assisted photoacoustic spectroscopy, white light nanoscopy, low-coherence phase-shifting interference microscopy, and Mirau interferometry.

Direct Two-Photon Excitation of Isomeric Transition in Thorium-229 Nucleus

A possibility of the two-photon excitation of an isomeric state in a nucleus of thorium-229 has been discussed. The fluorescence intensity of the excitation is demonstrated to be identical for the irradiation of nuclei with either monochromatic light or polychromatic radiation consisting of a sequence of short lightpulses of the same intensity. The two-photon excitation of Th3+ ion in an electromagnetic trap with a focused laser beam with a wavelength of about 320 nm and power of 100 mW can lead to the absorption saturation, at which the fluorescence emission with the frequency of the transition in a nucleus is maximal. In crystals doped with Th4+ to a concentration of about 1018 cm-3 and irradiated with a laser radiation 10 W in power, the emission of several photons persecond with a wavelength of about 160 nm becomes possible.

SPECIFICITY OF APPLICATION OF X-RAY METHODS OF «SWING» AND LAUE IN DETERMINING THE QUALITY OF THE STRUCTURE OF CASTINGS OF NICKEL HEAT-RESISTANT ALLOYS

Systematically analyzes and justifies the characteristics of equipment operating in monochromatic radiation by the «swing» method and in polychromatic radiation by the Laue method in relation to the specifics of controlled samples in the technology of single-crystal casting from nickel heat-resistant alloys. The main application of the «swing» method is the mass control of seed blanks, seedings, growth cones of samples and blades. The main application of the Laue method is local measurements of block misorientation in the casting of the turbine blade, determination of the crystallographic orientation misorientation in controlled areas on the blade. An optimized configuration is proposed for a compact modification of a diffractometer operating in monochromatic radiation for mass control of the structure in production.

Enhanced Tomographic Sensing Multimodality with a Crystal Analyzer

This article demonstrates how a combination of well-known tools—a standard 2D detector (CCD (charge-coupled device) camera) and a crystal analyzer—can improve the multimodality of X-ray imaging and tomographic sensing. The use of a crystal analyzer allowed two characteristic lines of the molybdenum anode—Kα and Kβ—to be separated from the polychromatic radiation of the conventional X-ray tube. Thus, as a result of one measurement, three radiographic projections (images) were simultaneously recorded. The projection images at different wavelengths were separated in space and registered independently for further processing, which is of interest for the spectral tomography method. A projective transformation to compensate for the geometric distortions that occur during asymmetric diffraction was used. The first experimental results presented here appear promising.

First laboratory X-ray diffraction contrast tomography for grain mapping of polycrystals

The first results of three-dimensional grain mapping using a laboratory tomograph equipped with a microfocus W target X-ray tube source, operated at 90 kV and 350 µA, are presented. Adapted algorithms exploit the polychromatic radiation spectrum and the projection magnification arising from the cone-beam geometry. The first map of grain shapes and crystallographic orientations from a titanium sample containing 42 grains is presented and its validity confirmed by a phase contrast reconstruction of the grain boundaries. Perspectives are given for the further development of the technique to accommodate samples with more grains or with greater intragranular orientation spread.